Placental chorioangioma: presentation of a case with electron-microscopic and immunochemical studies.

A case of placental chorioangioma in an infant who experienced transient congestive heart failure is presented. The mechanism for this heart failure was probably due to excessive left to right shunting of blood across the tumor. Electron-microscopic examination revealed the tumor to be composed of endothelial cells and vascular structures of different types. Immunochemistry revealed the lack of normal placental antigens indicating that these tumors are not composed of trophoblastic tissue.